This invention relates to a method of producing mat and rough sheetlike, ribbon-shaped or filiform polymeric products, preferably natural-fiber-like mat and rough textile products of chemical fiber materials, in particular of synthetic fiber materials or mat and rough polymer films having little transparency.
Synthetic fiber materials are distinguished from natural fiber materials by a variety of outstanding useful properties. Polyester and polyamide fiber materials occupy a preeminent positoin among synthetic fiber materials. The individual filaments of these two fiber materials are cylindrical and have a smooth surface (except for the small percentage of total production of profiled monofilaments spun with special dies). As a result, these fiber materials and the products made of them look glossy and feel smooth or soapy or greasy to the touch. Even fiber materials delustered in spinning still have a considerable gloss. In contrast thereto, sheetlike structures of natural fiber materials, especially of wool and cotton, have a mat appearance and a rough or woolly feel.
These differences in gloss and feel are particularly evident in the comparison of sheetlike structures of polyester or polyamide monofilaments with sheetlike structures of wool or cotton. Sheetlike structures of polyester fibers, on the other hand, come closer to natural fiber products in these properties. Variations in shape of polyester and polyamide fiber materials in the macroscopic range, for example, due to crimping or texturizing, result only in a minimal approximation to the dullness and feel of natural fiber materials. The same is true for fiber materials spun with profiling dies. Even in profiled monofilaments, the surface regions of individual filaments, reflecting light in one direction, are still too great to eliminate glossy effects. Crimping or texturizing does indeed make the filament and hence the sheetlike structure bulkier and softer; the smooth, soapy feel, however, is not appreciably influenced.
Roughening, abrading and methods derived therefrom are used in sheetlike structures of synthetic filaments to break individual filaments, usually in a special filamentary system, so that the broken ends project from the surface of the sheet and form a fibrous web. These broken ends, for one thing, produce a diffuse reflection of light, which imparts to the sheetlike structures a mat appearance, and, for another, they result in a soft woolly feel. However, the resultant velvety texture is only of interest for specific fields of application. In addition, these treatments require certain constructions of sheetlike structures; for example, smooth tight fabrics cannot be treated in this way. The low gloss and the woollier feel of sheetlike structures of yarns can be attributed to the filament ends projecting from the fibrous web. On the one hand, gloss and feel of textile sheetlike structures are properties dictated by fashion. On the other hand, high-quality textile products are generally considered to be those made of natural fiber materials.
The development of chemical fiber materials and their modification was and is, therefore, oriented toward the production of fiber materials and products which combine the new, useful properties with the tried-and-true, and traditional, properties of natural fiber materials. The demand for approximation of gloss and feel of synthetic fiber materials to those of natural fiber materials should be seen from this point of view.
Polymeric films, for instance of polyester, polyamide, polyethylene or triacetate, have smooth, in some cases glossy surfaces and a high transparency. These properties are disadvantageous for a variety of fields of application. It is known that films of limited size may be roughened on a vibrating table by scattered sand. This method, however, has the disadvantage that continuous roughening of endless webs or bands of polymeric film is not possible. In addition, it is known that structured film surfaces may be obtained by embossing with rolls which have a surface corresponding to the embossed pattern. However, gloss, feel and transparency of the films are not very much influenced thereby. According to one known method, a surface roughness may alternatively be obtained by addition of suitable material to coatings, e.g., by addition of rice starch to gelatine. This method, however, has the disadvantage that it is associated with coating of the sheet.
An object of the invention is to make chemical fiber materials, in particular synthetic fiber materials, more natural-fiber-like with respect to gloss and feel, whereby textile products produced from chemical fiber materials become higher in quality and polymeric films are made rough, mat and less transparent.
A further object of the invention is to produce, in novel fashion, chemical fiber materials having natural-fiber-like feel and gloss and mat, rough polymer films having little tranparency.